This invention relates to respirators in general and, in particular, to a new and useful gas humidifier for respirators which includes a vaporizer arranged in a housing for evaporating water into the respiratory gas and for feeding the gas to be wetted through the housing while the water is heated and for subsequently providing an additional heating of the gas at the vicinity of the vaporizer in accordance with the temperature of the gas as it is measured at the mouthpiece connection to the patient.